IR Laser Out of LPC-815

[ELEktron]

It is dim red on white paper

 

[sampson]

Yes, as ELEktron said, you can see it, but it's DECEPTIVELY dim looking.

The general consensus seems to be that 380nm-750nm constitutes "visible light" so 780nm is way out there but most people including myself can detect light up too at least 850nm as DARK red. So most people, if not all, can also see the common 808nm lasers.

Using this chart you can calculate the difference in perceptibility of one wavelength versus another:
1988 CIE Photopic Luminous Efficiency Function

Acording to that chart, if my math is correct, for the same light output, measured in mw, a 532nm green laser will be 58,997.3 times brighter in terms of how you perceive it. This is the reason that everyone warns to be very cautious with the NIR lasers.

Here is, basically, the same chart as a graphic via wiki:
File:Eyesensitivity.png - Wikipedia, the free encyclopedia

 

[Misellus]

I built one a few weeks ago. ~125mW at 150mA using a Aixiz driver (2 for $8 shipped off ebay)

It's a dim red dot that hard to see from more than 10 feet away, easily visible in the dark though. Just so you understand how dim this dot is, I thought I had LEDed the first 5 I played with since it was barely noticeable in a lighted room.

I just took some pictures but they did not come out as well as I'd hoped. Neither camera I have access to is IR filtered. So rather than a dim red dot you see a white one.

The three dots are 633nm from a HeNe, 650nm from a pointer, and 780nm from the 815 diode. The out of focus shot does a little better to show the color difference. Hard to believe the rightmost one is over 20x as powerful as the first two.

misellus

 

[sampson]

Awesome pics Misellus. The camera is way more sensitive to NIR than our eyes so the difference is even more dramatic in person.

 

[ELEktron]

I can see light up to 850nm

 

[LtKernelPanic]

Is there a consensus on a safe range to drive one of these diodes? I'm tempted to build an IR laser in the host I just ordered from mohrenberg. I was thinking of using one of the LM317s I have as a driver. I only have a few resistors on hand but if I did the math right a 10 and 30 ohm in parallel would give me a total of 7.5 ohms resistance or ~165ma which would be under the 180ma mentioned from the data sheet in the 9th post. Since these have the same pinout as the LOC from the sled making a case negative host would simplify the build a lot.

 

[Misellus]

I had one that took over 300mA though I've no idea how long it would have lasted since I removed it from the module and threw it away (as I mentioned, I thought it was bad since the dot was so dim). Then had one that died in about 10 seconds at 180mA which is why I went with 150mA.

Misellus

 

[Braddubya]

Is there anything that these can be used for besides burning? Ill probably build one just because I cant stand to throw away a diode but im hoping theres atleast something I can do with it.

 

[Benm]

The general consensus seems to be that 380nm-750nm constitutes "visible light" so 780nm is way out there but most people including myself can detect light up too at least 850nm as DARK red. So most people, if not all, can also see the common 808nm lasers.

Its very hard to call the relative brightnesses in the near-IR range, as they seem to very considerably between people. Most people will be able to see half a watt of 808 pump light projected on a piece of paper easily, but how bright it is percieved varies wildly.

But it is always deceptively dim - by the time 808 looks like even 1 mW of 650 nm, its definitely time to stop looking at it.

 

[rhd]

I'm sorry to revive a really old thread, but I think it's a lessor evil than starting a new one for this inquiry - has anyone come across a PIV curve for these LPC-815 IR 780nm diodes?

 

[RA_pierce]

I've run some above 325mW.
Funny thing is, the mode shifts erratically at high power. I've never seen this in a diode before.
Unfortunately, I never did think to graph the current vs. output.
You may be able to find a specification sheet for these diodes, though. If not for this specific diode, perhaps a data sheet for a similar diode (or a few) would give you a close enough approximation.

Edit: I didn't even realize until just now that I posted in this thread already.

 

[Flaminpyro]

@ rhd so you want to know the peak inverse voltage for these IR diodes ?